Film cassettes within which film is wound without any manual threading of the film onto a reel have long been known (and also have been called magazines, or simply packages). In a first type of cassette, film is wound without the use of a takeup reel, the film merely being coiled within substantially circular spring members of flexible material which expand with the coiling of the film. Examples of such cassettes can be seen in U.S. Pat. Nos. 1,799,184 and 2,381,033.
However, this first type of prior art cassette has several disadvantages. Firstly, strip material, such as film, coiled upon itself within a generally circular spring cannot be wound into as tight a configuration as can be achieved with a takeup reel and, secondly, and perhaps most importantly the frictional effect of the coil spring against the film being wound causes a binding of the film, such that the use of such magazines have been limited to films that are no more than approximately ten feet in length.
Cassettes or magazines wherein strip material is self-threaded upon a takeup reel have also been known for some time. Examples of such arrangements can be found in U.S. Pat. Nos. 2,878,283 and 3,550,882. In the arrangement described in U.S. Pat. No. 2,578,283, film is inserted into the cassette through an opening and is directed via a guide channel to a point where a spring or spring biased member presses the end of the film into contact with a takeup reel. The surface of the takeup reel is provided with a tacky adhesive on its periphery such that the end of the film will adhere to the takeup reel and thus can be tightly wound on the takeup reel upon rotation of the reel. However, the use of adhesive materials for retaining the lead end of the strip material to the takeup reel has the disadvantage that, with repeated use, the adhesive material loses some of its sticky qualities each time the film is unwound and removed from the cassette such that a point is reached when the takeup roller is no longer able to retain the lead end of the strip material. This effect requires replacement or discarding of the takeup reel, and results in jamming of the material within the cassette if the cassette is used without knowledge of the fact that the adhesive no longer has sufficient retaining capabilities.
In the self-threading cassette according to U.S. Pat. No. 3,550,882, a free end of a film having conventional sprocket holes along one longitudinal margin is guided to and into engagement with a takeup reel having matching sprockets. The threading guide is an arcuate spring-like member extending from an inlet opening of a cassette housing into resilient engagement with the takeup reel so that film entering the cassette housing will be guided to the takeup reel where the sprockets will mesh with the film after initial contact of the film with the reel. To prevent slack from developing in the film, which could cause its disengagement from the sprockets, a slipping type drive is utilized to rotate the cassette takeup reel at a speed that is faster than the speed at which the incoming end of the film is fed.
The self-threading cassette such as disclosed in U.S. Pat. No. 3,550,882 also has disadvantages. Firstly, and most importantly, such a self-threading cassette is limited to use with strip material, such as film, that has a longitudinal series of apertures running along one margin, and reduces the range of applicability of such a cassette. Additionally, due to the fact that the takeup reel is rotating at a speed faster than the incoming strip material, a sudden force will be applied to the apertures as the sprockets are initially engaged. Such a shock can damage the apertures and eventually lead to difficulties. On the other hand, should the apertures on the film fail to engage in the sprockets or become disengaged before the film is wound tightly upon the reel, threading and winding will not occur and jamming might occur since there is no guiding of the film strip after it is initially brought into contact with the winding reel.